Q: Low coolant light came on, just did a water pump in 2016 temps dropped on the east coast 2004 BMW 760i

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Coolant low light

My car has 94000 miles.
My car has an automatic transmission.

Hello - in the absence of any visible leaking coolant, it is quite likely the "low coolant" warning is the result in incomplete bleeding of air from the water pump replacement in 2016. If air was not bled out of the heater portion of the cooling system after the water pump service, using it these past weeks during cold weather opened up that circuit, and additional coolant was needed from the reservoir as the captured air bled out. BMW uses solenoid valves on this model to open or close coolant flow to the heater components, so any air in the heater circuit was pretty-well trapped there until the heater was used. Refill the reservoir, and watch closely for the need for additional coolant. Should the requirement for additional coolant persist, I recommend a coolant leaking inspection performed by a mobile, professional mechanic, such as one from YourMechanic, who will come to your location, diagnose this problem, and give you an accurate assessment of damage and cost estimate for repairs.

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